Radio receiver apparatus



Oct. 13, 1942. l D. H. MITCHELL 2,299,058

` RADIO RECEIVER APPARATUS Filed Aug.- 3, 1940 A.; y y? i Patented Oct. 13, 1942 T ENCE.

RADIO RECEIVER APPARATUS Donald H. Mitchell, Chicago, Ill., assigner to Galvin Manufacturing' Corporation, Chicago, Ill.,

a corporation of Illinois Application August 3, 1940, Serial No. 350,436

(Cl. Z50-14) 11 Claims.

My invention relates in general to radio receivers and more in particular to a portable radio receiver adapted to bel carried over the body of the operator, similar to a camera or field glasses, by means of a combination aerial and carrying strap.

Although portable receivers have been in commercial use for some time, there are disadvantages to the more usual type carried by a handle because one hand of the operator is entirely employed and he is somewhat inconvenienced in carrying packages, suitcases, or the like, which might be part of his equipment when the portable receiver is most popular, such as when traveling, on picnics, and the like. There has been some consideration in the prior art given to a receiver carried on the body of an operator so as to leave the hands free for operating the receiver while moving, or for carrying purposes. The operation of this latter type of receiver has not been satisfactory, however, because of an inability to provide relatively uniform and satisfactory reproduction over the wide range of operating conditions which might be encountered, and hence has not been used to any extent commercially until the present invention.

It is an object of my invention to provide an improved portable radio receiver adapted to be carried over the body of an operator soV that the hands are free for other uses.

Another object of my invention is to provide radio receiver apparatus including a portableV receiver and a combination carrying strap and loop antenna therefor which track with respect to one another in a manner such that satisfactory reproduction is obtained under many, and varied operating conditions.

A further object of my invention is to provide an efficient radio receiver which is little larger than a camera case and is carried over the shoull' der by a strap in the manner of a camera, or field glasses. v

A feature of my invention is the provision of portable radio apparatus with a receiver carried by a strap normally slung over the shoulder of the operator to leave the hands entirely free, with control and indicating means at the top face f the receiver in a position most available and oonvenienU for inspection and operation, and with the stra-p supporting the receiver in a manner such that the weight of the receiver and any force exerted during tuning is directed downwardly against the strap to provide a positive andl sturdy support.

Another feature of my invention is the provision of complete portable radio receiver apparatus with a superheterodyne circuit and associated elements, a loop antenna, all of such construction and having characteristics such that substantially uniform reproduction is obtained under wide variations in operating position of the antenna, and different body effects upon the apparatus due to variations in the electrical characteristics in the body of the operator wearing the apparatus. More specifically the complete system includes a loop antenna, and a superheterodyne receiver circuit having an I. F. transformer, and a tuned diode transformer, all of such construction, and having characteristics such that highly efficient apparatus is provided.

Another feature of my invention is the provision of a simplified strap antenna which is conveniently and comfortably carried over the shoulder of an operator, and which readily connects to the portable receiver and cooperates in effecting ready assembly and disassembly of the receiver apparatus.

A further feature is the provision of compact, rugged receiver chassis structure and housing, which utilizes the strap antenna for closing the housing, and yet permits ready removability of the chassis from the housing.

A still further feature of my invention is the provision of an improved combination loop antenna and antenna coil in a carrying strap for a portable radio receiver, with readily connectible contact means between such combination structure and the receiver circuit.

Other objects and features of my invention will be apparent from the following description taken with the drawing, in which:

Fig. l is a perspective view of the complete radio receiver apparatus.

Fig. 2 illustrates the manner in which the receiver apparatus is carried over the body of an operator.

l Fig.v 3 is a bottom plan view of the apparatus of- Figs. 1 and 2.

Fig. i is an enlarged detail view of a fragmentary portion of the antenna strap, housing, and receptacle on the chassis illustrating particularly the structiue of the strap, receiver housing, and chassis, associated with the connections between the antenna and the receiver circuit itself.

Fig. 5 is a cross-sectional view along the line 5-5 of Fig. 3, but illustrating only the strap structure.

Fig. 6 is a schematic illustration of the antenna portion and first two tube stages of the receiver system circuit.

In practicing my invention I provide portable radio receiver apparatus with the receiver chassis and power supply for the receiver circuit mounted in a single housing and carried over the body of an operator by a combination loop antenna and antenna coil incorporated into a carrying strap to be slung over the shoulder of the operator. The carrying strap includes concealed therein a combination loop antenna and antenna coil, with the ends terminating in Contact pins for engagement with corresponding sockets connected to the radio receiver apparatus. The carrying strap is secured to the housing of the receiver in a manner such as to insure contact between the loop antenna and the receiver circuit during use, and is of such a construction that the housing may be readily disassembled upon the removal of the strap from such housing. A superheterodyne circuit is employed for the receiver, and the loop antenna described above, is connected to such circuit. The receiver circuit and antenna have characteristics such that they are in continuous alignment over a wide range of different body effects acting on the loop among different operators when wearing the apparatus. The body effect is normally expected to change the inductance and capacitance of the loop. In broadening the operating characteristics of the entire system, the means for accomplishing this with the loop antenna include an I. F. coil unit, and diode coil unit in the receiver circuit, both of relatively high gain. However, the circuit is such that there is no overcoupling to provide the resulting undesirable operating conditions.

Referring now to the drawing, Figs. l and 2 illustrate the complete receiver apparatus in noncarrying and carrying positions, respectively. The apparatus includes a receiver housing IE] with a dial aperture I I on the top face surrounding a dial, and indicating mechanism, and a speaker opening I2 on the front face. Control knobs I3 are available on the top face of the housing adjacent the dial aperture. With the dial and control knobs at the top face of the housing they are most conveniently located for the operator for inspection and operation. As is shown in Fig. 2, the receiver apparatus hangs approximately at the waistline of the operator so that the dial and control knobs are not only in the most accessible and convenient location for operation, but any pressure that might be exerted downwardly on the top face while tuning is entirely taken up by the mounting for the housing on the combination unit I4 comprising a loop antenna and carrying strap. The receiver is carf ried by the strap I4 adapted to be slung over the shoulder of the operator as shown in Fig. 2. The strap includes a covering I6 (Fig. 5) of simulated leather or the like, closed along its edges by tape-like pieces II sewed to the covering, and a multi-turn loop aerial or antenna within the covering comprising an insulated wire I8 looped over the length of the strap and laying in a substantially single plane as shown in Fig. 5. One end of the wire extends into and is appropriately secured to a pin I9, while the other end is similarly secured to a pin 2|. The pins are mounted on a member 22 of still" insulating material, by eyeletting or the like to secure each pin on the outside of the strap adjacent the ends of the loop. The member 22 is doubled over and stapled at 23 at the ends thereof to encircle the strap.

The receiver chassis illustrated in general by dotted lines in Fig. 1 and indicated by the reference character C is mounted within the housing I0 and removable therefrom through the open bottom which is normally closed by a cover 24. Screws S under the strap and on opposite sides of the chassis extending through the housing wall and into the chassis retain the chassis in the housing. The cover 24 is retained on the upper portion of the housing by means of a strap 25 secured at one end to such upper portion at B, and passing over the carrying strap at the contact pin portion. The strap 25 snaps onto the cover at 26 and at 2'I (Fig. 3), and onto the main or upper portion of the housing at 28. The carrying strap itself passes through oppositely disposed loops 29 on the side of the housing as shown in Figs. 1 and 2, and can be pulled down through such loops so as to pull the bottom of the strap away from the cover portion 24 of the housing and provide ample room for the removal of such cover, and then the removal of the chassis from the housing. At the same time, with this construction the Weight of the receiver apparatus presses the housing toward the lower loop in the strap I4 to assist in holding the strap I4 on the housing, holding the housing together, and maintaining good electrical contact between the antenna and receiver circuit through the pins I9 and 2I, and corresponding sockets I9 and 2I on the receiver chassis. Such sockets are mounted on a terminal strip 30 which in turn is supported by the receiver chassis with access to the terminal strip, through the cover 24 being obtained through an aperture A.

One commercial embodiment of my invention Y includes a 4-tube superheterodyne receiver, of

which the rst two tube stages alone have been illustrated in Fig. 6. The last two stages, the A and B battery supply, and the speaker portions, are substantially conventional for a portable battery operated receiver and these are not illustrated. The rst tube stage 3I, as illustrated in Fig. 6, comprises a pentagrid converter with the grid 32 of the R. F. section in series connection with the antenna loop indicated by the reference character I8 corresponding to the previously described designation for the wire I8 in the carrying strap. The connection is made through the pin I9 on the loop and the corresponding socket I9' on the chassis. The antenna resonant circuit extends from the loop through socket I9', and through one gang 33 of the variable condenser to ground. The circuit then extends from ground through an AVC by-pass condenser 34, and lead 35 to socket 2 I and pin 2|. At the same time the grid 32 is connected into the circuit and the capacity of the grid as well as the capacities of the wire leads in the circuit are effectively a part of the capacity of the condenser gang 33. l

As to the circuit determining the oscillator frequency and hence the range of frequencies over which the receiver may be tuned, this includes an oscillator grid coil 33, the other gang 3'I of the two gang variable condenser, a trimmer condenser 38, and a condenser 39 to prevent a direct current path to ground. At the same time the condenser 39 allows the R. F. current to enter the oscillator grid of the tube 3l, which grid is designated by the reference character 4 I. Actually the condenser 39 has substantially no effect on the oscillator frequency or tracking. A grid leak 42 is connected to ground in the usual manner.

A plate coil 43 is in electrical connection with the B -I- terminal, and to a plate of the oscillator portion of the tube 3| to provide the necessary feedback for oscillation. The second tube 44 illustrated diagrammatically in Fig. 6 is an I. F. amplifier, and an I. F. transformer 46 is employed intermediate the tube 3| and tube 44.

The loop antenna I8 in the carrying strap I4 during the use of the portable radio apparatus of the present invention is placed in various operating positions. In Fig. 1, for instance, the complete apparatus is illustrated as setting on the ground, a table, or the like, with the loop antenna haphazardly placed in a somewhat bunched position. The loop, as illustrated in Fig. 2 is subject to body effects of the wearer, and in addition operates normally, and has a greater signal pickup because of the more extended position of the loop. The effect of the proximity of the body to the loop is to change the capacity and inductance of the loop. This body effect will assume various proportions on different persons, and will operate differently so far as signal pickup is concerned depending upon the direction in which the operator is moving, or standing.

In the attempts prior to the present invention to provide a portable receiver with an antenna carried on the body of the person, the receiver would operate differently on different persons, and vary according to the position of the antenna, with all of these various conditions either destroying or improperly eifecting the tracking between the oscillator coil 36 and the loop antenna. The result of this mistracking was to either reduce the signal voltage so that reproduction was poor and distorted or reduce the signal voltage to the place where reproduction was inaudible. In the present radio apparatus the I. F. channel has been broadened out materially in contrast to the normal range of channel width in a superheterodyne so that in one embodiment the width is as much as 50 kc. for the present receiver, as contrasted with 15 kc. for a normal superheterodyne. In other words, theoretically the receiver is less selective.

than might be the case with a normal superheterodyne circuit, but actually the fact that the selectivity curve has been broadened out provides better reproduction over the entire broadcast range of frequencies. It is understood that the difference in reproduction will vary depending upon the position of the loop and the operator, as explained above, but the average results will apply as above.

The I. F. channel is broadened out in the circuit to provide a broader selectivity curve by means including the I. F. transformer 66 having comminuted iron cores il and lll for the coils i8 and e8', respectively. Coil i8 is connected to the grid G of the tube 44 and ground, while coil 48 is connected to the plate P of tube 3| and to B+. This construction provides a high permeability core which permits the use of less wire in the coils themselves making for a smaller diameter. This relatively small diameter for the coils is 3A, and inch for the coils d8, and lS, respectively, in one commercial embodiment. Inasmuch as space is a very important factor in the complete apparatus the small diameter of the coils permits the use of a relatively small shielding can 49,

while a considerable space is still maintained bei' tween the coils and the can. This spacing increases the Q of the coils, and with the high permeability cores provides a gain of 60 for this unit.

The two coils d3 and 48' are adjusted to slightly.

over optimum coupling to provide the widest possible acceptance band for the particular transformer. The high Q of the unit acts to improve skirt or sideband selectivity. A pair of trimmer condensers T are mounted at the top of the can 49 and connected to the coils e3 and d8 as shown.

A diode coil unit 52 likewise assists in providing a broader selectivity curve to improve the general operating results. Unit 52 includes a pair of coils 53 and 53', with coil 53 connected intermediate the plate P' of the R. F. amplifier tube 44, and the plate coil 43. The coil 53' is connected to the plate of the detector tube, which latter is the first tube stage not illustrated in the circuit diagram, and to the A. V. C. portion of such tube. In one embodiment the coil 53, and 53', are approximately 5A; inch and inch in diameter, respectively. A ccmminuted iron core 54 for the coils 53 and 53 raises the Q and gain of the coil unit to Sli and permits the use of relatively small coils. A trimmer condenser T is mounted in the unit and connected to the coil 53 as shown. The comminuted iron sleeve encloses coils 53 and 53 and acts to spread the side bands, as well as broaden the frequency response curve, so that the peak is broadened without at the same time getting a so-called hump in the curve. The overall gain of the receiver is 540,000 (voltage gain). The sleeve 56 does not affect the Q or gain of the coils but it does provide very close coupling without undesirable overcoupling. This close or increased coupling broadens the selectivity of the coil unit, and reduces the magnetic field about the coils. As a result, a very small and tight fitting shield 5l can be applied to the sleeve. This materially conserves space in the complete receiver, which is important in maintaining a small compact unit. Normally this tight and substantially pressed t for the shield on the sleeve would deleteriously affect the shielding, but inasmuch as the sleeve 56 already shields the coils, the can or shield 51 is merely supplementary for shielding purposes. A zinc plate 58 is applied to the bottom of the can. With a tight compact unit 52, mounting on the receiver chassis is facilitated, and all of the shielding prevents leakage from the coil units to other components of the receiver. With the loop i8 around the housing l0, such leakage would be equivalent to feeding signals back to the loop, and would cause oscillation in the set or receiver.

As to the loop antenna I8, this is in reality a low Q loop as a result of the fabric around the loop in the carrying strap i4, and an increase in resistance of the loop over normal values as a result of the proximity of foreign matter such as the battery, or batteries within the receiver, the metal chassis, and various components thereon. These are all within the field of the loop and hence reduce the current flowing through the same, as a result of the loop passing around the receiver apparatus. The relatively low Q loop reduces the selectivity and hence broadens the resonance curve of the loop but this is desirable because then the body effect of various operators does not have such a critical effect on the tuning. With a sharp peak on the selectivity curve, slight changes in the position of the loop, changes in body effect, and the like, would cause mistracking and reduce the signal voltage within the loop, to in turn reduce the effectiveness of reproduction as discussed above.

From the above description it is clear therefore that the present invention provides a compact, sturdy receiver apparatus which is carried very conveniently and comfortably by a combination loop antenna and carrying strap for the receiver apparatus. ,A relatively broad superheterodyne circuit is provided, such that the receiver is not undesirably critical to various operating conditions and positions of the loop antenna therefor. Where normally the broadness would deleteriously affect the gain of the receiver, in the present invention the high overall gain has not been sacrificed and most satisfactory reproduction is obtained. In describing the invention in the specification and claims, radio apparatus is used to designate the entire structure illustrated in Fig. 1, comprising receiver apparatus with the related chassis, circuit, and housing, and the combination antenna and carrying strap combined as a single unit for supporting the receiver apparatus, and supplying signal energy to a receiver circuit.

Although the invention has been illustrated and described in its preferred embodiment, it is understood that the invention is not limited thereby, but is limited only by the scope of the appended claims.

I claim:

1. In portable radio apparatus adapted to be carried on the body of an operator and including a radio receiver chassis and circuit, means for carrying said apparatus and receiving signals for said circuit including a hollow carrying strap, a loop aerial mounted in said strap, and means for electrically connecting said loop aerial with said receiver circuit and physically connecting the same with the receiver chassis including a pin Contact on each end of said loop, insulating means for substantially rigidly supporting said pins in an adjacent insulatingly separated position on said strap at right angles thereto, and contact receptacles insulated from one another on the receiver chassis releasably retaining said pins, with said pins extending inwardly into said receptacles, and with said strap supporting said apparatus adjacent said pin supporting means.

2. In a portable radio receiver including a housing with an open-ended portion having a receiver chassis supported therein and a cover for said open end, the combination of means for carrying said housing with the chassis, and means for releasably retaining the carrying means on said housing, said carrying means including a strap having thereon a loop aerial, a contact member secured to each of the two ends of the loop for connection with the receiver chassis and relatively stiff insulating means for supporting said contact members on said strap and insulating them from one another, with said strap being positioned over the outside of said cover and with said strap retaining means including a strap member secured at both ends to the open-ended housing portion with one of said ends being releasable, and said strap member having a portion intermediate said ends extending over the cover and over the strap to retain the latter thereon.

3. In a portable radio apparatus in-cluding receiver apparatus and a housing therefor, a combination unit including a carrying strap and a loop antenna thereon, with said carrying strap secured to said housing and having a portion extending above the same and a second portion extending under the housing, with the housing bearing downwardly against said second portion, and a plurality of contact means insulated from one another and electrically connected to the loop antenna for connecting said antenna to said receiver apparatus including a plurality of means connected to said loop antenna, insulated from one another, and extending upwardly from said combination unit under said housing for connecting with the receiver apparatus in the housing, with the downward pressure from the weight of the housing being applied downwardly against the combination unit to assist in maintainingthe connection between the loop antenna and the receiver apparatus.

4. Portable radio apparat-us adapted to be carried over the shoulder of an operator with the receiver apparatus therefor positioned approximately at the Waistline of the operator, the combination of a receiver housing for said receiver apparatus having top, bottom, and oppositely disposed side faces, a receiver chassis within the housing, a combination member including a carrying strap and loop antenna for carrying over the shoulder of an operator and extending over the two oppositely disposed side faces of the receiver housing, means for maintaining the combination member on the two oppositely disposed side faces with a portion of said member extending over the bottom face of said housing and supporting the housing in a manner such that the weight of such housing and the chassis therein will bear downwardly against said portion of said combination member, means connecting the loop antenna in the combination member to the receiver chassis extending up- Wardly from the combination member through the bottom face of the housing to the receiver chassis, with the weight of the receiver chassis and the housing bearing downwardly against the connecting means to maintain such connection, and means at the top face of the housing for tuning the receiver apparatus from a position readily available to the operator for a visual inspection and manual operation, with the mounting of the receiver apparatus in the combination member likewise supporting downward pressure on the housing when tuning the receiver circuit at the top face surface.

5. In portable radio apparatus having straplike carrying means adapted to be carried over the shoulder of an operator to support the receiver apparatus therefor approximately at the waistline of the operator, the combination of receiver apparatus including a housing having a bottom face and a top face, a receiver chassis Within the housing, tuning and indicating means at the top face of the housing available for visual inspection and ready manual operation by the operator, and means for carrying and supporting the apparatus substantially at the waistline of the operator in a comfortable position for such operator and with the tuning and indicating means readily available thereto, such carrying and supporting means including a combination carrying strap and loop antenna for the radio receiver apparatus with a portion of said combination strap and antenna passing under the housing, means operatively retaining the housing thereon so that the weight of the housing and the pressure for tuning is applied downwardly on said combination member, and means extending inwardly from the loop antenna into the chassis to connect the antenna and receiver apparatus.

6. In portable radio apparatus adapted to be carried on the body of an operator with a portion extending over the shoulder of the operator, the combination of radio receiver apparatus including a circuit therefor, said circuit comprising a superheterodyne circuit including an intermediate frequency transformer having a pair of magnetically coupled coils and a comminuted iron core for each coil, and a diode coil unit comprising a pair of coils having a comminuted iron core therefor, a comminuted iron sleeve surrounding both of said coils in said diode coil unit, and a metallic shield entirely around the outside of said iron sleeve, and a loop antenna adapted to be carried over the shoulder of an operator and subject to the body effects thereof, said antenna being of low Q and connected to said receiver circuit for feeding signals thereto with said antenna and receiver circuit tracking in a manner to provide substantially uniform reproduction under many different operating conditions in the portable apparatus resulting from different body effects acting on the antenna when the apparatus is carried on an operator.

7. In a portable radio apparatus adapted to b-e carried on the body of an operator, the combination of a strap-like loop antenna adapted to be carried over the shoulder of an operator when transporting the apparatus as portable equipment and operating in various positions on and oif the body of an operator, and subject to varying body effects among various operators when carried on the body of an operator, connecting means extending from said loop antenna for electrically connecting the antenna to a receiver circuit and a receiver with a circuit connected to said loop antenna, a housing for said receiver, with the loop antenna extending below said housing to support said housing thereon, said receiver having connecting-means-receiving-means within the housing to connect the antenna and circuit, said receiver having a superheterodyne circuit therefor having such components and such characteristics that substantially uniform -reproduction is obtained over all o-f such various operating positions for said loop antenna both on the body of an operator and off the body of an operator, such circuit including an intermediate frequency transformer having a pair of coils, comminuted iron core means for said coils, and a diode coil unit comprising a pair of coils, comminuted iron core means for said coils, a comminuted iron sleeve tting over said coils in substantially coaxial alignment therewith, and shielding means around said sleeve.

8. In portable radio apparatus adapted to be carried on the body of an operator with a portion extending over the shoulder of the operator, the combination of a strap-like loop antenna adapted to be carried over the shoulder of an operator when transporting the apparatus as portable equipment and operating in various positions on and olf the body of an operator, and subject to varying body effects among various operators when carried on the body of an operator, and a receiver connected to said loop antenna having a superheterodyne circuit therefor having such components and such characteristics that the selectivity curve for said circuit is broadened without sacrificing overall gain in the circuit to thus provide substantially uniform reproduction over all of such various operating positions for said loop antenna both on the body of an operator and off the body of an operator, such circuit including a converter tube and an intermediate frequency transformer connected thereto having a pair of coils, iron core means for said coils, an intermediate frequency ampliner tube connected to said transformer, and a diode coil unit connected to said amplifier tube having a pair of coils, iron core means for said coils, and an iron sleeve fitting over said coils, with said transformer having a gain substantially of 60 and said diode coil unit having a gain substantially of 60.

9. Portable radio apparatus subject to various operating conditions due to the various positions in which it is employed as portable equipment, including in combination a loop antenna, a strap housing said loop antenna and serving as a carrying strap adapted to be extended over the shoulder of an operator for said apparatus, and a radio receiver having a housing with said strap housing passing under said receiver housing and supporting the same thereon, circuit means in said receiver housing electrically connected to said loop antenna, pin contacts on the inside face of said strap housing electrically connected to said loop, extending through said receiver housing and connected within said receiver housing to said receiver circuit, and means in said radio receiver in combination with said loop antenna in the carrying strap for providing satisfactory reproduction in said receiver in all of the numerous operating conditions to which portable radio apparatus is subjected, and at the same time maintaining a relatively small compact unit for easy portability, including in said receiver circuit an intermediate frequency transformer having relatively small comminuted iron cores, coils therefor, an-d a relatively small shielding can for said transformer, and a diode coil unit including a pair of coils, a comminuted iron sleeve for said coils to closely couple the same, and being of a relatively small size to provide a relatively small unit, said sleeve also providing shielding for said coils.

l0. In portable radio apparatus adapted to be carried on the `body of an operator, the combination of strap-like carrying means of insulating material having an antenna concealed therein and having a face thereon, pin contact means connected to said antenna and positioned on said face of the strap-like carrying means, a housing having a top face, and side and bottom faces, a

Areceiver chassis including electrical circuits within the housing, with said strap-like carrying means extending over the bottom and side faces of said housing with said strap-like carrying means face in engagement therewith, with said contact means extending through said housing and connected to the receiver chassis within the housing, with the position and connection of said contact means being such as not to short circuit electrical circuits of the chassis, tuning and ndicating means at the top face of the housing available for visual inspection and ready manual operation by the operator, means retaining the housing supported on said strap-like carrying means so that the weight of the housing and the pressure for tuning is applied downwardly onto said strap-like carrying means extending over the bottom housing face.

ll. In portable radio apparatus adapted to be carried on the body of an operator and including a housing, and a radio receiver chassis and circuit having pin contact receiving means therein, the means for carrying said apparatus and receiving signals for said circuit including a hollow carrying strap having an inside face, an aerial mounted in said strap, and means for electrically connecting said aerial with said receiver circuit including a pair of pin contacts electrically connected to said aerial, stiff insulating means on the inside face of said strap rigidly mounting said pin contacts thereon, means for securing said stiff insulating means to said strap, with said pin contacts adapted for connection with said pin contact receiving means, and said strap being looped downwardly for supporting the housing thereon and on the inside face thereof.

DONALD H. MITCHELL. 

